import java.util.Arrays;
import java.util.Scanner;

import org.korifey.ffalg.NumberTheory;
import org.korifey.ffalg.Probabilities;


public class Problem15 {
	
	public static void main(String[] args) {
		System.out.println(solve());
	}

	final static int n = 20;
	
		
	public static long solve() {
		return Probabilities.combinationsByPascalTriangle(2*n, n);
	}
	
}
